The invention relates to a displacement pump with an oscillating method of operation, particularly adapted for the pumping of a dense or abrasive liquid medium or one containing solid particles. More particularly, this invention relates to an oscillating displacement pump which is preferably equipped with a piston drive which is acted upon by a hydraulic pressure medium and drives a displacement unit wherein the piston drive has a constant or adjustable stroke or stroke frequency.
Embodiments of pumps are known which are unsatisfactory with respect to guiding the flow of a pumped medium, their operating behavior, and their ease of maintenance of the entire pump. For example, in a known pump, the suction and pressure valves are positioned at the same height at opposing points in the housing jacket of a cylindrical pump housing. This design requires that the entire medium be pumped through the pump housing and thus past the displacement unit itself. In addition, this arrangement requires a four part, right angle turn-around of the pumped medium, with a turn-around in each valve housing. The known flow guidance through the pump not only results in an increased pressure loss within the pump, but also subjects all structural pump parts which are exposed to the full flow of the pumped medium to increased wear.
With such a pump, self-acting ventilation of the displacement unit housing through the valves, particularly during startup of the pump, is not possible since the valves are located at about the same height and positioned diagonally relative to the direction of motion of the displacement unit. In the known pump, the displacement unit has the form of a plunger piston. In addition, there is a pump in the displacement unit housing beneath the plunger piston. The sump can only be emptied by means of time-consuming measures on the part of the maintenance personnel.
Other known pumps of the general type initially mentioned display either all or some of these disadvantages.